Means for increasing the effective head of water produced by a dam during flood stages of water.



L.- F. 'HARZA. v MEANS For: mcnusme THE EFFECTIVE HEAD or WATER PRODUCED BY A DAM mmms FLOOD STAGES or WATER.

APPLICATION FILED OCT. 6. 1916.

Patefited Apr, 16, 19 18.

V LEROY F. HABZA, OF PORTLAND, OREGON.

MEANS FOR INCREASING THE EFFECTIVE HEAD OF WATER PRODUCED BY A DAT-4 DURING FLOOD STAGES OF WATER.

Specification of Letters Patent.

PatentedApr. 16, 1918.

Application filed October 6, 1916. Serial No. 124,150.

useful Means for Increasing the Effective.

Head of WVater Produced by a Dam During Flood Stages of Water, of which the following is a specification.

This invention relates to means for increasing the effective head of water produced by a dam during flood stages of water.

It is well known to hydraulic engineers that the level of the water below a dam,

known as the tailwater, usually rises con-i siderably faster, as the result of floods, than thelevel of the water above the dam, known as the headwater, thereby correspondingly reducing the effective head or difference in level between headwater and tailwater available for producing power.

As is well known, also, it is frequently necessary to supplement the water power plant required for developing the full capacity of a dam at a normal water stage, in order to provide necessary power during flood stages. This is done either by providing additional water power units or by means of a steam or other auXiliary plant, the comparative cost thereof usually determining which shall be used. Also, under some conditions, the effective head is so greatly reduced as the result of floods that the turbine will not run atnecessary speed, thus rendering resort to a steam or other auxiliary power plant absolutely necessary.

The object of the present invention is to provide improved means for increasing the effective head of water at flood stages and thus increasing the power developed at flood stages and correspondingly reducing the auxiliary power equipment and cost thereof necessary for keeping the capacity of the power station up to normal;

As my invention relates to means for car rying out my improved process, the invention consists in providing a spillway for the dam constructed and arranged to form a hydraulic air compressor; in providing means for confining the water discharged from the water wheels to form an upwardlymoving column of water; and in introducing air, distributed 1n the form of bubbles, into said column of water at or'near 1ts lower. end, thereby reducing the specific gravity of the water and correspondingly reducing the back pressure on the power. unit due to the weight of said column of water.

My invention also comprises the various other features, combinations of features and detailsof construction hereinafter described and claimed. I

In the accompanying drawings, in which my invention is fully illustrated,

Flgure 1 is a cross sectional view of a dam having an open splllway.

Fig. 2 1s a cross sectlonal view through a power unit taking water from said dam,

equipped with head regaining means of my invention.

Fig. 3 is a view similar to Fig. 2, illustrating a modification as it relates to the introduction of the air intothe water column at the lower end of the draft tube of said water power unit.

Fig. dis a view similar to Fig. 1 of a section of said dam constructed to form an air compressor and accumulator.

Fig. 5 is a fragmentary view from the position 55 of Fig. 2, showing the air distribution pipes; and v Fig. 6 is an enlarged detail sectional side View on the line 6-6 of Fig. 2, of preferred: forms of air admission and air discharge pipes used for introducing air bubbles into the water.

Referring now to the drawings, in which I have illustrated a novel form of dam constructed and arranged for effecting the object of my invention as it relates to my improved process of increasing the effective head of water in a water power plant at stages of flood water, A, Fig. 1, designates an open spillway form of dam, a. the normal water level above thedam, or headwater level, a the normal water level below the dam, or tailwater level, a the headwater level at flood stage, and a the tailwater level at} flood stage, the difl'erence between the flood tailwater level and the normal tailbe assumed in the specification. In other cases, however, the water flows through a canal from the dam to the power house, entailing a drop of headwater level and of tailwater level at the power house below that at the dam. This fact in no way affects the application of my invention, but merely introduces a complication which I avoid by the assumption stated.

"The effective head of water at a normal stage is the vertical distance between the normal headwater level a and the normal tailwater level [0 while the effective water head at flood stage is the vertical distance between. the flood headwater level a, and the flood tailwater level a As the power developed by a water wheel is a direct function of the effective head of water, and as the vertical distance or head between the flood water levels (0 a is materially less than between the normal water levels a, a it is obvious that, under the conditions assumed, the power developed by a. water wheel at. a flood stage of water will be less than the power developed by said water wheel at a normal stage of water; In fact, the power developed varies as the 3/2 power of the head and, therefore, the loss of power is proportionately greater than the reduction in head.

The power unit B, as a turbine water wheel, is installed in a suitable channel which communicates with the upstream side of the dam A, Fig. 1, as usually constructed, and the power developed thereby is trans mitted by the shaft Z; which extends up-. wardly to a desired point of application, being, as shown, connected directly to an electrical generator, indicated at B To render the power unitconveniently accessible for repairs and other purposes, said power unit B is preferably located somewhat above ihe normal tailwater level a the used water from said power unit B escaping through a discharge tube B commonly known as a draft tube, which communicates with the discharge side of the power unit and extends downwardly below the normal tailwater level a so that the water discharged through said draft tube will create a suction on said power unit which will compensate for the position'of the power unit above the normal tailwater level 06, in a familiar manner.

In accordance with my invention, I provide means for confining the water discharged from the draft tube B during flood stages, to form a column of'w-ater' flowing upwardly from the lower or discharge end of said draft tube, the upper end of which is preferably substantially level with the flood tailwater level. Convenient means for thus confining the water discharged from said draft tube consists of usualgates B the ends of which are fitted to grooves 6 formed in piers B at each side of the discharge end of said draft tube so as to slide therein' The column thus produced will tend to produce a back pressure on the draft tube B? substantially equal to the height of the flood tailwater level above normal and the means for producing same may be de scribed in a general way as means for extending the lower or discharge end of the draft tube upwardly. This upwardly extending channel may be of uniform size in cross section, or its size in cross section may increase upwardly if found to be economically desirable or necessary under special conditions. In Fig. 2 of the drawings, the

water column formed by the gates B is of uniform cross-section, said gate extending substantially parallel with the face ofthe power house foundation. In Fig. 3 of the drawings, however, said water column is shown as increasing in size upwardly, which is effected in a simple and inexpensive manner by flaring the gate B upwardly away from the face of the power house foundation.

In order to reduce the back pressure on the power unit B due to the weight of the column of water represented by the height of the flood tailwater level above normal, I provide means for introducing air into the column of water formed at the discharge end of the draft tube by the gates B at or adjacent to its lower end, said air being introduced in such manner that it will be distributed throughout said column in the form of bubbles. Said air bubbles will operate, in an obvious manner, to reduce the specific gravity of the water forming said column, thus correspondingly reducing the back pressure on the power unit B as compared with the weight of a solid column of water represented by the difference in level between the normal and the flood tailwater levels, thus reducing the loss of power due to loss of effective head substantially in the ratio of the specific gravity of the air-impregnated water forming said column and of a solid column of water of the same height. For purposes ofillust'ration let'us assume that the water impregnated with air bubbles forming the water column at the discharge end of the draft tube 13 weighs only two thirds as much as that of'a solid column of water ofthe same height. With this relation, it is obvious that the back pressure on the power unit will be reduced approximately one third, and the loss of power will be reduced in even greater proportion since,

at the discharge end of the draft tube subof water, but so that it will be actually greater thanthe effective normal head of water, by extending said draft tube any desired distance below tailwater level and correspondingly increasing the height of the column formed by the water dischar ed from said draft tube and introducing the air bubbles at or near the lower end of said col umn of water, it being necessary only toobserve the requirement or condition that the distance of the power unit B above the effective tailwater level a shall not exceed the height of a column of water which will be sustained by atmospheric pressure, or about 30 feet. In this case the comparison will be between a solid column of water from the point of admission of the airto theflood water level and the same column impregnated with air, in the manner previously eX- plained. Thus, assuming that the length of the upward moving water column formed by the water discharged from the draft tube is.

twenty-four feet and, as before, that the weight of a water column impre nated with air bubbles is only two thirds of the weight of a solid column of water of the same height, the effective head of water would be increased eight feet, and if the loss of effec tive head due to the flood stage of water is only four feet, an actual gain of four feet in effective head would be produced.

In Figs. 2 and 3 of the drawings, 1 have shown two different constructions for introducing air into the water column.

As shown in Fig. 2, an air supply pipe 1 is supported near the lower end of the draft tube, being embedded in the foundation of the power house at the upper side of the draft tube B projecting laterally from which, across the upward moving column of water at the discharge end of the draft tube .15 are branch pipes 2 provided with holes or openings 3 on their upper sides, through which the air contained in said suply pipe 1 and branch pipes 2 will be discharged into the column of water above said pipes. As best shown in Figs. 5 and 6, said branch pipes 2 and the air discharge holes therein are spaced apartand arranged to produce a substantially uniform distribution of the air discharge holes or openings 3 across said channel or column of water. While the distribution of the holes or openings 3 admits of a considerable range of variation, what I now consider to be a preferable arrangement and relation is one in which said holes will be spaced about three inches (3) apart in both directions over Obviously, howedges of said air discharge pipes 2 which are the entire crossv section of said channel or ascending water column. Also, in order that an adequate supply of air may be furnished to all of said air discharge openings 3, said air discharge pipes 2 are preferably tapered toward their outer ends, and in order to reduce the obstruction which they form to the flow of the water .npwardly through the channel formed by the gates B the lower presented to the current of water, are tapered, as shown at 4. Also, to render the action of the column of water in and the current of the water flowing through said trunk uniform, the distributing air pipes 2 are preferably arranged so that the sides thereof in which the air discharge openings 3 are formed will all be substantially in the same horizontal plane.

As shown in Fig. 3, the air supply pipe, designated 1 is positioned at the lower side of the draft tube B and airv is discharged therefrom into the lower end of the water column formed by the gates B by means of a plurality of small branch pipes 5, which extend from said air supply pipe 1 through the floor of thedraft tube B Said air supply pipe 1 is preferably positioned somewhat back of the extreme lower or discharge end of said draft tube proper, the relation being such that the current of water in said draft tube and trunk will carry the air bub bles into the column of water formed by the gates B and will effect a substantially equal distribution ofsaid bubbles over the entire cross section of said column.

While I consider the arrangements of air supply and air distributing pipes shown and described in said Figs. 2 and 3 as preferable,

other constructionsv and arrangements for introducing a r distributed 1n the form of small bubbles through the water column formed by the gates B will readily suggest themselves to hydraulic engineers and I do not, therefore, desire to limit myself to the particular constructions and arrangements shown, as my invention contemplates any arrangement and construction of air supply and distributing pipes for attaining the objects sought. 1

lVhile the described increase of effective head and thus of power will be secured by ing the effective head at stages of flood, water to compensate for the loss of power due to the loss of effective head on account of such flood stage of water, would exceed the cost of installation and operation of a usual form of steam or electrical auxiliary plant for supplying the necessary power to compensate for the loss of power due to the loss of effective head at flood stages of water. But, at flood stages of water when large quantities of water are running to waste, it is possible to utilize such waste water by a simple form of hydraulic air compressor to accunnnulate a sufficient quantity of air under sufficient pressure for the purpose and practice of my invention at such relatively small cost that a large economy will result therefrom.

In Fig. 4 of the drawings, I have shown, in cross section, a form of air compressor adapted for utilizing waste water discharged over. the dam for accumulating and compressing air to be used in the practice of my invention.

Referring now to said Fig. 41, A designates a section of the dam A, Fig. 1, and, as in said Fig. 1, a designates the normal headwater level, a the normal tailwater level, a the flood headwater level, and a the flood tailwater level.

The section of the dam A is provided with a closed'spillway 6 of proper size to supply the necessary quantity of air, in the manner presently described. The upper side 7 of the entrance end of said spillway is preferably slightly below the normal headwater level a and what may be described as the crest of said spillway, designated 8, is at or slightly above said normal headwater level, so that at normal stages of water and slight variations therefrom, no water will be discharged through said spillway 6. At its lower end, the spillway 6 communicates wit-h a closed chamber or compartment 9, the outer wall 10 of which forms a water seal for said compartment 9 and extends a sufficient distance below the level at which air is discharged fro-m theair pipes 2, Fig. 2, or 5, Fig. 8, into the ascending column of water formed by the gates B at the discharge end of the draft 7 tube B to produce an air pressure in said chamber sufficient to overcome the pressure produced by the weight of the column of water formed by the gates B above said air distributing pipes 2 or 5, as the case may be, the friction in the air conveying pipes and other causes of loss of pressure. Also, the lower wall or side of the spillway 6 is preferably extended upwardly within the chamber 9, somewhat above the lower edge of the front wall- 10- of said compartment.

In the preferable construction shown, the spillway 6 is constructed in the form of a curved Venturi tube, the admission and discharge ends of which are flared and the size of which adjacent to the crest 8 thereof 1S reduced to form a contracted throat, wherenot necessary for the successful operation of w my invention and my invention contemplates equally a spillway of uniform cross-section.

Supported adjacent to the crest 8 of the spillway 6 and extending lengthwise of the dam section A, is an air intake pipe 11, the ends or other points of which are open to the air and which is provided with branch pipes 12which extend across the spillway 6 at or near the crest of said spillway. As shown, said pipes 12 are similar to the branch pipes 2, except that they are inverted from the position shown in Fig. 6. As shown, also,said air intake pipe 11 is embedded in the wall of the spillway directly below the crest 8 thereof and said branch pipes 12 extend across the section of said spillway at the discharge side of the contracted throat thereof, and are provided with holes or openings corresponding to the holes 3 in the pipes 2 except that they are formed in the under sides of said branch pipes 12, whereby the flow of water through said spillway 6 will produce a suction which will operate to draw air from said pipes 12 into the water flowing through said spillway, distributed in the form of bubbles, which will be carried by the current of water into the chamber or compartment 9, where it will accumulate under increasing pressure until it bubbles out underneath the wall 10, unless conveyed away and used as it accumulates.

If desired, my invention contemplates, as an alternative construction, embedding the air supply pipe in the position shown in dotted lines at 11 Fig. 4.

With the described construction, it is obvious that the air pressure in the chamber 9 at any time will be equal to the weight of a vertical column of water equal in height to the difference between the level of the flood tailwater a and the water level 13 within said chamber 9, plus the additional pressure required to cause the water to escape through the opening 14, the maximum pressure obtainable in said chamber at any given stage of flood water being equal to the weight of a column of water equal in height to the vertical distance between the flood water level a and the bottom of the outer wall 10 of said chamber 9.

The air chamber 9 is connected with the pipe 1 or 1 by means of a pipe 1 which forms an extension of one or the other of said pipes 1 or 1 as the casemay be, and

which is connected directly with said air chamber 9 by means of. a pipe or pipes 15, said pipe 1 being preferably located at a higher elevation than said chamber and said connecting pipe 15 communicating with said chamber at or adjacent to the top thereof.

t the beginning of the air compressing operation by the spillway 6, the water level 13 within the chamber 9 is the san'ie as'the water level in the tailrace. As the air brought down through said spillway accumulates in the chamber 9, however, this difference in level will become progressively greater due to the increased volume and pressure of the air in said compartment until the height of the unbalanced column of water produced thereby is equal to the vertical depth of the air distributing pipes 2, Fig. 2, or 5,.Fig. 3, below flood tailwater level, and further increase in height of said column will cause the air contained in said chamber 9 to flow therefrom through the pipes 15, 1 l or 1 to'the air distributing pipes 2 or 5, as the case may be, from which it will escape through the holes in said air distributing pipes into the ascending column of water formed by the gates B Thus, by making said chamber 9 of suflicient depth below the flood tailwater level a and correspondingly extending the lower wall 10 of said chamber below said flood tailwater level, the air in said compartment may be compressed to any extent desired.

As shown, the air admission pipes 12 are substantially identical in construction with. the air discharge pipes 2 and are installed in substantially the same relation to each other, except that the angular edges thereof are disposed upwardly so that they will be presented to the current of water p'ssing through the spillway 6, and the air discharge openings therein are formed in the under sides thereof.

The air chamber 9 may represent either a single chamber, common to all of the power units B, or separate chambers for each of said power units, the sizes of the air distributing pipes being so proportioned, in either case, that substantially equal quantities of air at substantially uniform pressure will be delivered into the ascending column of water formed at the discharge end of the draft tube of each power unit. To effect this end, various systems of piping can readily be supplied by skilled engineers, and it is not, therefore, necessary to describe any particular system in detail.

Although not essential to the principle of my invention, it would be convenient and desirable to have various valves and gates suitably located to regulate the amount of air compressed, the amount of water discharged through the spillway, the amount of air'admitted to the rising column of water, etc. The location and arrangement of said valves admits of a wide range of variation to meet diiferent conditions, and in any partlcular case can readily besupphed by skilled mechanics without a detailed de scription thereof.

I claim 1. The combination of a dam, a water.

power unit taking water therefromv and means for increasing the eflective head of water produced by said dam at said water power unit, said means comprising means for confining the water discharged from said water power unit to form an ascending column of water, and means for introducing air into said column of water, substantially as described.

2. The combination of a dam, a Water power unit taking water therefrom and means for increasing the effective head of water produced by said dam at said water power-unit,sa1d means comprising means for confining the water discharged from said water power unit to form an ascendlng and 4:- The combination of a dam. a water a power unit taking water therefrom and means for increasing the effective head produced by said dam at said water power unit, said means comprising means for confining the water discharged from said water power unit to form an ascending column of water, and means for introducing air into said column of water near its lower end distributed in the form of bubbles, substantially as described.

5. The combination of a dam, a water power unit taking water from said dam. and means for increasing the effective head produced by said dam at said water power unit, said means comprisinga hydraulic air compressor constructed and arranged to be operated by surplus water flowing over said dam, means for confining the water dis charged from said water power unit to form an ascending column of water, and an air transmission pipe which communicates with said air compressor and with said water column below the discharge level of said water column. substantially as described.

, 6. The combination of a dam, a water power unit taking water from said dam. and means for increasing the effective head produced by said dam at said water power unit, said means comprising a hydraulic air compressor constructed and arranged to'be' operated by surplus water flowing over said dam, means for confining the water discharged from said water power unit to form an ascending column of water, and an air transmission pipe which communicates with said air compressor and a plurality of small distribution pipes which connect said air pipe with said water column below the discharge level of said column of water, substantially as described.

' 7. The combination of a dam, comprising a section having a closed spillway, a chamber into which said sp'illway discharges,

spillway will create a suction operating to draw air through the air dischargeopensaid air in the form of bubbles into the water flowing through said spillwayand will carry said air into the chamberintd which said spillway discharges, a water'power unit which takes wa-ter"fro1n -saiddam,; means for confiningthe water discharged from said water power unit'toform an ascending column of water, an'air transmis sion pipe supported adjacent tothe. lower end of said water'colum-n which communicates with the air space of the chamber into which the air impregnated water from-the closed =sp1llway of said dam is discharged,

and-a-plurality of relatively small distribution pipes whiclrconnect said air transmission pipe with said watercolumn' below the discharge level ofsaid column of water, substantially as described.

ings in the discharge pipesicommunicatmgr with said air supply pipe and will i-lnt'roduce 8. The, combination of adam comprising a section having a closed spillway, the end sections of said spillway channel being flared and the portion thereof adjacent to the crest of said spillway being contracted, a chamber into which said spillway discharges, said chamber being formed with closed top and side walls and being provided with a water discharge opening below the top thereof, an air intakepipe supported adjacent to the crest of said spillway,

and'branch pipes which project from said air intake pipeinto said spillway provided wlthfalr discharge openings, the relation be ;ing;.such that water flowing through said spillway will create a suction operating to draw airthrough the'air discharge openngs n the d1scharge pipes communicatlng with sa d airjsupplypipe and will introduce i'said air in the form ofbubbles into the wa terfiowing through said spillway and will carry said'air' into the chamber into which said spillw-ay discharges, a water power unitfwhi'ch' take-s water from said dam, -means for confiningthe water discharged from saidwater power unit toform an ascending column of wat-er, anair transmis- -S10I1. p1;p6 supported adgacent to the lower endof said water colum'nwhich communi- 'cat'es with :the a r space of the chamber. into whlch thea1r1mpregnated water from the 'closed spillway of said dam is discharged,

and-a plurality of-relatively small air distri- -bution' -pipesf wl1icl connect said air pipe -w1th said water column below the discharge level of said column of water substantially as described.

In testimony, that claim the foregoing as my invention, '1 afliX my signature in the presence of two subscribing witnesses this 21stday of September A. D. 1916;

I L. F. HARZA.

Witne'sses:

WILLIAM H. WETZLER, J. BQBINGHAM,

Qopiee crime patent may be obtained for. five centseach ny addressing the Commissioner of Patents a v H Washington, 13.6. 

